Calcium

Other name(s):

General description

Calcium is the most abundant
mineral in the human body. It’s the main part of bone. But it is also needed for blood
vessels to contract and dilate, and for muscle functions. It helps send nerve impulses
and control nerve irritability. It also helps to clot blood. Calcium is also an enzyme
cofactor. It aids the endocrine and exocrine glands. Most calcium is a building block
of bone and tooth enamel. This is called calcium hydroxyapatite.

Medically valid uses

Calcium is extra important in times
of bone growth. These include childhood and adolescence. It’s also needed during
pregnancy, when breastfeeding, and after menopause.

You need calcium to make breast
milk. A baby in the womb also needs it to grow.

Not getting enough calcium in
puberty and adulthood may lead to osteopenia and osteoporosis. These conditions cause
weak bones that may break easily.

Unsubstantiated claims

There may be benefits that have not
yet been proven through research.

Calcium may lower the risk of
colorectal cancer. It may also help reduce the risk of heart disease. It may lower blood
pressure. It may also ease menstrual cramps and help manage weight. Calcium may help to
prevent preterm labor and birth.

Recommended intake

Calcium is measured in milligrams
(mg). It’s absorbed by the small intestine. But only part of the calcium in foods and
supplements is absorbed.

The Recommended Dietary Allowance
(RDA) by age is:

Group

RDA

Infants (0 to 6 months)

200 mg

Infants (6 months to 1 year)

260 mg

Children (1 to 3 years)

700 mg

Children (4 to 8 years)

1,000 mg

Youth (9 to 18 years)

1,300 mg

Adults (females 19 to 50 years; males 19 to 70 years)

1,000 mg

Adults (70+ years)

1,200 mg

Women

50 years and older

1,200 mg

Pregnant or lactating, 18 years or younger

1,300 mg

Pregnant or lactating, 19 to 50 years

1,000 mg

Calcium in supplements most often
come in 2 forms. These are carbonate and citrate. Carbonate needs stomach acid to be
absorbed. It should be taken with food. Citrate is more easily absorbed. It can be taken
with or without food. People with low stomach acid should take this kind. This includes
older adults.

Calcium is available in oral
tablets. Doses range from 250 to 1,200 mg. It also comes as oral chews, capsules,
powders, wafers, and liquids. Your body absorbs calcium the best when the dose is 500mg
or less at 1 time. That means if you want to get 1000mg a day, take 2 500mg doses at
separate times of day. Vitamin D helps your body absorb calcium.

Calcium exists in nature only with
other substances called compounds. These compounds contain different amounts of
elemental calcium. This is the actual amount of calcium in the supplement. Calcium is
found in many products. Each form has a different amount of calcium. Calcium carbonate
and calcium phosphate have the highest amounts of calcium. Calcium gluconate and calcium
glubionate have the lowest.

Calcium-rich foods

Food

Calcium (mg)

Fortified oatmeal, 1
packet

350

Sardines, canned in
oil, with edible bones, 3 oz.

324

Cheddar cheese, 1.5
oz. shredded

306

Milk, nonfat, 1
cup

302

Milkshake, 1 cup

300

Yogurt, plain,
low-fat, 1 cup

300

Soybeans, cooked, 1
cup

261

Tofu, firm, with
calcium, 1/2 cup

204

Orange juice,
fortified with calcium, 6 oz.

200–260

Salmon, canned, with
edible bones, 3 oz.

181

Pudding, instant
(chocolate, banana, etc.) made with 2% milk, 1/2 cup

153

Baked beans, 1
cup

142

Cottage cheese, 1%
milk fat, 1 cup

138

Spaghetti, lasagna,
1 cup

125

Frozen yogurt,
vanilla, soft-serve, 1/2 cup

103

Ready-to-eat cereal,
fortified with calcium, 1 cup

100–1,000

Cheese pizza, 1
slice

100

Fortified waffles,
2

100

Turnip greens,
boiled, 1/2 cup

99

Broccoli, raw, 1
cup

90

Ice cream, vanilla,
1/2 cup

85

Soy or rice milk,
fortified with calcium, 1 cup

80–500 (varies)

Calcium is stable in foods. It
doesn’t break down with storage or cooking.

You may need more calcium if you have any of the below:

A malabsorption syndrome, such as sprue or celiac disease

Pancreatitis

Cirrhosis of the liver

Lactose intolerance

Milk allergies

Anorexia

A vegetarian diet that doesn’t include eggs or dairy

Moderate to heavy alcohol or caffeine intake

Calcium is absorbed best by the
body when it’s taken several times a day in amounts of 500 mg or less. But taking it all
at once is better than not taking it at all. Calcium carbonate is absorbed best when
taken with food. Calcium citrate can be taken anytime.

Calcium supplements are used to
treat calcium-deficiency problems. These include:

Tetany of the newborn

Kidney problems, including
end-stage kidney disease

Thyroid issues

Osteoporosis and softening of
the bone (osteomalacia)

Rickets

Chronic calcium deficiency leads to
poor bone mineralization. It also causes decreased bone growth and repair. In young
adults, this may lead to osteomalacia. In older adults and post-menopausal women, it may
lead to osteoporosis. In children, it’s linked with rickets. This is often due to both
vitamin D and calcium deficiency.

Tetany occurs when the serum level
of ionized calcium becomes too low. This causes muscles to contract and stay contracted.
This condition happens due to an acute decrease in ionized calcium in the blood. It’s
often a result of hyperventilation.

Side effects, toxicity, and interactions

High levels of calcium in the blood
is called hypercalcemia. This rarely happens from eating too much calcium from foods.
It’s more likely to be caused by calcium supplements.

Excess calcium intake (2 grams or
more) may cause calcium deposits in muscles. This may cause stiffness and pains. Calcium
deposits can also show up on heart valves. This can cause fatal heart damage. Calcium
deposits are more likely to happen when you also have a high vitamin D intake. Be
careful not to take more than 800 mcg/day of vitamin D, especially when taking calcium
supplements.

Consuming large amounts of calcium
with milk or an antacid can cause milk-alkali syndrome. This can cause hypercalcemia. It
can also harm your kidneys.

You shouldn’t take calcium supplements if any of the below apply to
you:

Your serum calcium levels are too high

Your phosphate levels are too low

You have kidney failure

You plan to have dialysis

You are taking thiazide diuretics such as HCTZ,
hydrochlorothiazide, or indapamide

You get kidney stones

Women who are pregnant or
breastfeeding should talk to their healthcare providers before taking any
supplements.

Calcium also interacts with certain
medicines. These include:

Tetracycline antibiotics

Norfloxacin

Verapamil

Calcium also reduces how well the
body absorbs iron. You shouldn’t take calcium at the same time as iron. You can do so
if the calcium is calcium citrate, or if you take the iron with vitamin C. You
shouldn’t take any medicine that needs to be taken on an empty stomach with calcium
supplements. Calcium limits the absorption of magnesium, iron, and zinc. High levels of
vitamin D may cause you to absorb more calcium.

Additional information

Calcium is the most commonly used supplement. It’s the easiest one to use. It also helps prevent osteoporosis.

Over 40 million people in the U.S.
have osteoporosis or have a high risk for the condition. These factors increase the risk
for osteoporosis in women:

Being thin or underweight

Having an eating disorder, such as anorexia nervosa

Chronic dieting

High alcohol or caffeine intake

A diet lacking in calcium

Keeping a healthy weight during adolescence can help prevent osteoporosis as an adult. Getting regular exercise can also help. Choose high impact activities, such as running or lifting weights.

Women who get their first menstrual period at a younger age or go through menopause at a later age have a lower risk of osteoporosis. Making sure you get enough calcium and vitamin D throughout your life can also lower your risk of the condition.

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